Medium-sized larva, 5-7 mm long. Head capsule rounded-oval; cephalic index 0.75-0.95. Dorsally, S5 slightly anteromesal to S7; S7, S8, DP near transversely aligned. Ventrally S10 posteromedial to S9, VP posterolateral to SSm, SSm, S9, S10 more or less aligned diagonally. SSm plumose; S7 plumose, strong; S8 thin, simple; S9 simple, strong; S10 simple, thin.
Almost 1/3 longer than mandible. Antennal ratio about 7.0. Basal segment about 4.5-6.3x as long as basal width, with ring organ at 0.75; segment 2 short, 2.5-3.0 as long as wide; segment 2 and 3 separated by wide, intersegmental region, equal in length to peg sensilla, appearing as a 3rd segment (of 5); segment 3 small, as long as wide; apical segment slender, 3x as long as segment 3. Style conspicuously to unusually long and wide, at least half as long as segment 2. Blade almost as long as flagellum. Accessory blade reaching to segment 3.
Slender, smoothly curved. Apical tooth 2 x as long as basal width, almost 1/3 length of mandible. Mola extending into apically-directed slender point, with small accessory tooth; long seta subdentalis arises between mola and accessory tooth. Ventrolateral seta 1 simple, 2 simple or branched, and 3 multi-branched to plumose; Ring organ midway between SII and SIII.
Basal segment of palp squat, 2.2-2.5x as long as wide, with ring organ about midpoint.
With sparse fringe of swim-setae. With 4 anal tubules. Procercus about 3.5-4x as long as wide, with 10 apical setae. Posterior parapod with 10-17 claws, up to 4 small claws expanded basally.
Brundiniella, a member of the tribe Macropelopiini, shares with Macropelopia and Bethbilbeckia an apparently 5-segmented antenna that actually comprises 4 segments: the expanded membranous intersegmental area between segments 2 and 3, flanked by peg sensilla, resembles a 'true’ segment (Niitsuma, 2003). Brundiniella may be distinguished from Bethbilbeckia and Macropelopia by the squat basal palp segment, and particularly by the uniquely widened base of some small posterior parapods claws and the expanded, bluntly pointed, innermost tooth of the pecten hypopharyngis.
Larvae of Brundiniella eumorpha live in cool brooks and springs in North America. Another species, known as larva only, occurs in the Sierra Nevada mountains of California: it is differentiated by the 3-4 (rather than 1) basally dilate, small claws of the posterior parapod. Larvae of B. yagukiensis, the second described species in the genus, occurs in sandy substrates in a low order, forested stream, in Fukushima Prefecture, Japan (Niitsuma, 2003). A larva and unassociated pupa of Brundiniella found at 1000 m. altitude in n. Thailand (P.S. Cranston pers. obs.) constitutes a first record for the Oriental region. Records from Brazil require verification.